We present the clinical cases of 2 girls, 5 and 10 years old, who presented with post natal growth retardation, mental retardation, scarce hair, body hirsutism, coarse facies, brushy eyebrows, broad nose, long filtrum, wide mouth, micrognathia, scoliosis, distal brachydactyly, prominent finger pads and hypoplastic 5th fingernails. Both patients had a normal blood cariotype, 46XX. The clinical characteristics are consistent with the diagnosis of Coffin-Siris syndrome, a genetic disorder of which there are less than 100 cases reported. Although the inheritance is apparently autosomal dominant there is still discussion about the exact mode of inheritance. The Coffin-Siris syndrome should be considered in the differential diagnosis in cases of children with mental retardation associated with coarse facies